Knee joint: Bursae and extracapsular ligaments (anterior view) (English)

Knee bursae are small fluid-filled sacs whose function is to reduce friction and accommodate gliding of muscles or tendons as they cross over bony prominences of the knee joint. Two groups of bursae are associated with the knee joint: bursae around the patella (anterior/patellar ligaments) and bursae located elsewhere. The nonpatellar group consists of a group of superficial bursae, most notable being the inferior subtendinous bursa of biceps femoris muscle and anserine bursa. The former is located on the lateral side of the joint, between the tendon of biceps femoris and fibular collateral ligament. The anserine bursa is found on the medial side, cushioning the space between the tibial collateral ligament and combined tendinous expansions of the sartorius, gracilis and semitendinosus muscles (pes anserinus).As many as fourteen bursae may be present, including the subtendinous bursa of iliotibial tract found between tibia and the distal part of iliotibial tract.The extracapsular ligaments of the knee are located outside the joint capsule. They are the patellar ligament, fibular and tibial collateral ligaments, and oblique and arcuate popliteal ligaments (depicted on the posterior view).